1. Technical Field of the Invention
This invention relates to cellular telecommunications networks, and more particularly to a method for handling global challenge authentication registration, and to a Mobile Switching Center (MSC) and a mobile station performing such global challenge authentication registration handling.
2. Description of Related Art
Ever since their introduction on the market, mobile stations have changed the way people communicate. Now, it is possible to reach a person almost anywhere, using only one number. The number is no longer linked to a location, but is rather linked to a mobile station that communicates through a radio interface with a cellular network. So wherever the mobile station is located, i.e. within the cellular network coverage, it can originate or receive a call by means of the radio interface. For originating a call through the cellular network, the mobile station has to identify itself by providing its Mobile Identification Number (MIN) and Electronic Serial Number (ESN). The MIN/ESN allows the cellular network to recognize which mobile station is calling, so to charge fees incurred for the call appropriately.
A problem that has emerged with the ever-increasing popularity of mobile stations is the cloning. The cloning is performed by “listening” to the radio interface to find a MIN/ESN, and programming a second mobile station with the same MIN/ESN. By doing so, the fees incurred for calls originated by the second mobile station are charged to the first mobile station. This method of fraud has caused important financial damages to cellular network providers and to owners of mobile stations.
To solve that problem, the security of cellular networks has been improved with authentication procedures to which the mobile stations must participate. One of the various authentication procedures that has been developed for D-AMPS (Digital-Advanced Mobile Phone Service) is called Global Challenge. This authentication procedure relies on using an algorithm called CAVE, and in an exchange of parameters between the mobile station and an authentication center. The authentication center stores a set of data for each mobile station including their MIN and ESN, along with an A-key and a Shared Secret Data (SSD) also called authentication data. The set of data is used as input parameters to the CAVE algorithm, along with a random number broadcast by the MSC servicing the mobile station, to verify authenticity of the mobile station.
More precisely, the Global Challenge procedure is performed on digital or analog control channel at system access, and involves validation of the authentication data received from the mobile station. System access is performed when the mobile station initiates or receives a call, or when the mobile station makes a periodic registration, typically every 10 minutes when the mobile station is powered on and idle, to inform the cellular network of its location.
However, when the mobile station is powered on, idle, and static for long periods of time, the periodic registration is continued with its repetitive global challenge performance, thus causing important processor load to the MSC. Furthermore, by repetitively performing global challenge at periodic registration while being static and idle, the risks of cloning the mobile station are increased due to the foreseeability of the periodic registration and the lack of movement and activity of the mobile station.
In order to overcome the disadvantage of existing solutions, it would be advantageous to have a method, which would allow better handling of the global challenge authentication performed in conjunction with the periodic registration. It would also be advantageous to provide a MSC and a mobile station that would support such better handling of the global challenge authentication at periodic registration.